WASHINGTON  In a practice that goes virtually unchecked, a new analysis suggests customers are buying, with a mouse-click, what appear to be illegal new ivory trinkets by thousands.

The sale of most new ivory was banned in 1989 to curb the slaughter of elephants in Africa. The ban has been instrumental in the species' recovery in several nations. Consumers in the U.S. still can legally buy items like chess sets and cutlery fashioned from antique ivory as long as the sales are accompanied by permits and certification documents.

Americans have the world's biggest appetite for ivory, along with the Japanese and Europeans. And a new, burgeoning clientele has conservationists especially worried  the rising middle class in China.

Investigators for TRAFFIC, a wildlife trade monitoring network, say they found more than 1,000 ivory items advertised each week on eBay and other auction Web sites. More than one-third of the merchandise specifically was described as elephant ivory. Few pieces carry even a pretense of documentation, they said.

Officials for eBay said they pull listings for illegal and unethical items, but ivory is subject to complex regulations. The online marketer said it is working with law enforcement and conservationists to improve its procedures.

Just filtering online listings that mention the word "ivory" would eliminate legal commerce for items such as "ivory-colored wedding dresses" and Ivory Soap memorabilia.

"There is no way that we can say for sure whether a listing for a piece of ivory is legal or not," said eBay spokesman Hani Durzi. "We don't ship merchandise or vouch for its authenticity or its source."

Online analysts said e-commerce can threaten rare species because transactions are easy and relatively anonymous. But conservationists could use some of the same online technologies to spotlight offenders.

"People around the world could be creating powerful networks to find out who is selling the illegal stuff and calling attention to them," said Lee Rainie, director of the Pew Internet and American Life Project in Washington, D.C.

Most of the ivory items were carved in China, investigators said, but they are being shipped to the United States through as many as 80 different countries.

The report by the wildlife group  described as the first of its kind since the ivory trade ban was adopted  also shows that U.S. customs agents seized more than 8,300 ivory items at airport and border checkpoints in a seven-year period ending in 2002. Most were cheap souvenirs bought by tourists who said they were unaware of the trade ban.

Conservationists calculate that, based on the number of items seized and sold, as many as 4,000 elephants, hippos and other ivory-bearing animals are being killed each year for their tusks.

They said U.S. law enforcement was doing a "good job despite limited resources" of spotting illegal imports through conventional channels. However, they said the new online markets were operating with "little oversight."

"Over the past 10 years, there has been a huge explosion in online vendors," said Simon Habel, director of TRAFFIC, the trade monitoring network supported by the World Wildlife Fund and other groups.

"When we posed online as potential buyers, ivory sellers in Shanghai and Guangzhou assured us that getting ivory into the United States would be no problem," Habel said.

The report was issued in anticipation of next week's meeting in Bangkok of the Convention of International Trade in Endangered Species of Wild Flora and Fauna, or CITES.

Before the ivory trade ban, poachers were slaughtering 100,000 elephants a year and threatening the species' existence in Kenya and other African nations.

In its report, the wildlife group examined 1995-2002 seizure data from the U.S. Fish and Wildlife Service and other federal agencies. They also did Internet searches February through May with online ivory sellers, posing online as potential buyers. They stopped short of buying illegal ivory items.

They also interviewed customers who bought ivory online and later claimed they were unaware of the trade ban.

"You could have extensive e-mail conversations and get a good feel for what's going on," Habel said. "The vendors would tell us, 'Don't worry, we can get a product in by labeling it as a bone carving. If it gets seized, we'll just send you another one.'"

Habel said TRAFFIC shared its results with law enforcement agencies and eBay.